Antenna construction with low q radiators

ABSTRACT

AN ANTENNA CONSTRUCTION WHEREIN THE RADIATOR ELEMENTS OF A RADIATING ARRAY INCLUDE SIDE-BY-SIDE ELONGATED PORTIONS WHICH HAVE BEEN SPREAD APART INTERMEDIATE THEIR ENDS SO THAT THE SEPARATION BETWEEN THE TWO ELONGATED PORTIONS OF EACH RADIATOR ELEMENT IS AT ITS GREATEST IN A GENERAL REGION MIDWAY BETWEEN THE CABLE-SUPPORTED OUTER AND INNER ENDS OF THE RADIATING ELEMENT.

United States Patent Inventor Harry C. Broyles Sunnyvale, Calif.

Appl. No. 770,285

Filed Oct. 24, 1968 Patented June 28, 1971 Assignee Granger AssociatesPalo Alto, Calif.

ANTENNA CONSTRUCTION WITH LOW Q RADIATORS 6 Claims, 15 Drawing Figs.

U.S.Cl 343/792.5,

343/807, 343/812, 343/886 Int. Cl ..B01q 11/10 Field at Search 343/7925,

[56] References Cited UNITED STATES PATENTS 2,524,993 10/1950 Rumsey343/807 3,165,748 1/1965 Woloszczuk 343/7925 3,271,774 9/1966 Justice343/7925 3,470,559 9/1969 Radford 343/7925 Primary Examiner- EliLieberman Attorney-Flehr. Hohbach, Test, Albritton & Herbert PATENTEUJUN28 19m SHEET 1 [IF 5 INVENTOR. HARRY C. BROYLES ATTORNEYS PATENTEUM28 as?! SHEET 2 1F 5 INVENTOR.

HARRY C. BROYLES ATTORNEYS PATENT0JuH28|9n 3,588,904

" SHEET 3 [IF 5 INVENTOR HARRY c. BROYLES ii ANTENNA cons'jrjaucrnoswrra sow o aanm'rons ascsoaouno or THE mvanrron This invention pejrtains to antenna structures. The invention is particularly useful, as alog periodic antenna of the type characterized by flexible dual wireradiator elements as may be supported at their ends by a flexiblecatenary cable.

As is Itnown, it has long been a general objective in providing logperiodic antennas and other similar types of antenna to reduce the bulltan physical scope of the antenna so that, among other things, theoccupied land space required for the installation will be minimized.

Where weather conditions are particularly adverse, it is also desirableto keep the antenna size to a minimum so as to reduce the expense landsize of the supporting structure as required, for example, to maintain aradiating array atop a support tower. Thus,,as is known, antennas ofthis type may be subject to icing conditions whereby the sail area ofthe radiating array becomes unmanageable and imposes serious burdens onthe supporting strdcture.

OBJECTS It is a general objefct of the present invention to provide animproved antenna structure and, more particularly, to provide such animproved antenna structure wherein the scope and size of the antenna isgenerally smaller for comparable per formance so as to require minimumsupport structure for the array.

It is another obje c i of the invention to provide an antenna structureof the above type wherein the Q of the radiator elements is reduced andthereby permits the radiating array to be commensurately reduced in sizefor comparable performance.

Other objects of the invention will become more readily apparent fromthe following detailed description when considered in conjunction withthe accompanying drawings.

SUMMARY OF THE INVENTION According to the structures herein disclosed,an antenna array has been provided having radiator elements comprised ofside-by-side spaced elongated portions carried from their outer ends andcoupled to feed line means at their inner ends. The array ischaracterized in the fact that intermediate the ends of the adjacentradiator portions, means have been provided for spreading the radiatorportions so as to reduce the Q of the radiator element.

In the above manner, the extent of the radiator element can be reducedwith the advantages attendant such reduction in the size of the array.Thus, less sail area is exposed to icing and weather conditions,catenaries supporting the array can be of smaller diameter, and therequired stretching forces applied to the catenaries can be reduced.Also, less occupied land space will be involved, as well as lighterweight materials and structures.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan view of anantenna array construction according to the invention;

FIG. 1A is a schematic perspective view diagrammatically showing anantenna construction according to the invention;

FIG. 2 shows, in enlarged detail, a plan view of a single radiatorelement of the type shown in FIG. I;

FIG. 3 shows, in enlarged detail, a plan view taken along the line 3-3of FIG. I;

FIG. 4 is a side elevation view of FIG. 3, partially broken away;

FIG. 4A is a view similar to FIG. 4 showing another embodiment of theFIG. 6 construction;

FIG. 5 is an enlarged detail plan view taken along the line 5-5 of FIG.I;

FIG. 6 is a front elevation view of a portion of FIG. 5;

FIG. 7 is an enlarged side elevation detail view taken along the line7-7 of FIG. ll;

FIG. 3 and 9, both taken along the line 3-8 of FIG. I, are enlargeddetail plan and front elevation views, respectively;

FIG. I0 is a schematic plan view of an antenna construction according toanother embodiment of the invention;

FIG. II is an enlarged detail plan view taken along the line II-lll ofFIG. I0;

FIG. I2 is a side elevation view ofa portion ofFlG. II;

FIG. I3 is a schematic perspective view of an antenna constructionaccording to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Having in mind the abovegeneral summary of the invention and with reference particularly to theaccompanying drawings, a detailed description of an antenna structureaccording to the invention can be more clearly understood with referenceto FIGS. I and IA. Thus, a support tower II carries a log periodic,transposed dipole array I2 comprised of a plurality of spaced elongatedflexible radiator elements 13. Each radiator element I3 includes a pairof elongated flexible porlions Id, Id.

The array 112 is supported atop tower II by a pair of catenary cablesI7, Iti carried by the ends of three equiangular support booms I9, 2I,22, respectively. Cables I7, I8 support the outer ends oieach of theradiator elements I3 while the inner ends of radiator elements I3 areoperatively coupled to feed lines 23, 24. The booms are inclinedupwardly.

Suitable guy wires 26 support the tower II in an upright position whilea mast extension portion 27 provides an anchoring point for guy lines 23acting to support the booms 19, H, 22 from above. Thus, array 12 liesabove the upwardly inclined booms.

With the foregoing arrangement in mind, there has been disclosed hereinmeans for interconnecting adjacent radiator elements I3 along a line ofconnecting, points defined intermediate the outer and inner ends of theradiator elements so as to provide a predetermined spacing between theportions Id, I6 of each radiator I3. The spacing is at its greatest foreach radiator I3 in the intermediate zone located between the outer andinner ends of the radiators and, for example, preferably issubstantially midway between the outer and inner ends of each radiatorelement. Accordingly, by inspection of FIG. 1, the aforementioned lineof interconnecting points is designated by the phantom line 29.

By spreading the two portions 14, IIIS of each radiator element fromeach other, it is possible to significantly reduce the Q of eachradiator element and in that manner broaden the bandwidth of the activeregion of the radiating array.

As is known, the Q represents a figure of merit of an energy storingsystem equal to:

21r(average energy stored energy dissipated per half-cycle).

The above fonnulation has been reduced for inductance whereby Q=,,L/Rwhere R is the equivalent series resistance of the inductors. Forcapacitance, Q is equal to 1/,,,CR.

The outer ends of elements I3 are supported by connection to cables I7,I3 as shown in enlarged detail in FIGS. 2, 3 and 4 as now to bedescribed.

Portions M, 116 of an element 13 are defined by separate reaches of asingle continuous electrically conductive flexible cable material suchas copper or aluminum wire.

A metal strap forms a stirrup 31 engaging the outer loop formed betweenportions M, 16 and the ends of strap or stirrup III are bolted orotherwise suitably secured to an end of an electrical insulator 32.Insulator 32 is of suitable material whereby it provides considerablephysical strength for supporting the outer end of element 13 andsuitable insulator material is, of course, well known to the trade. Forexample, the material of insulator 32 can be alumina.

The other end of insulator 32 carries a pair of support links 33pivotally secured to bar 32 and also to lobes 34 formed on each of apair of relatively thick plate portions 36 forming a cable clamp adaptedto be secured firmly to one of the catenary cables I7 I8. Each plate 36includes a recess portion 38 whereby screws 39 can draw the confrontingside faces of plates 36 tightly together to engage cable 18.

Lobe portions 34 may also be drawn tightly together whereby a bolt 41can pivotaliy support the end of each of the two links 33. Various meansmay be arranged for securing the outer end of each radiating clement I3to be carried by a catenary cable such as cables l7, I8 and anotherembodiment of the scheme for supporting the outer ends of elements 13 isshown in FIG. 4A.

In FIG. 4A, parts similarly employed to those previously described arenumbered the same but are provided with prime marks However, while theupper portions of plates 36 may be drawn tightly together with screws 39so as to clamp tightly against cable 18, the lobes 42 are spacedsomewhat apart whereby they provide an accommodating space or passage 43through which a loop formed in the outer end of a radiating element 13'can be carried directly by clamp 37'. It is to be understood, however,that clamp 37 will, accordingly, be constructed of an insulatingmaterial having sufficient rigidity to provide the support involvedherein. One such material, for example may be alumina or other highstrength insulating material.

Thus, the portions 14', 16' of a given radiator element 13 may beclamped together by a swage fitting 46 to provide a loop to engage theshank of a bolt 44 carried by the spaced lobes 42. In the foregoingmanner, it is apparent that the outer ends of each radiator element l3may be supported in an insulated fashion from one of the catenary cablesI7, 18.

As shown best in FIGS. 8 and 9, the inner ends of each radiator element13 are operably coupled to receive radiation from feed lines 47, 48 andit is to be understood that the pattern of selection of makingconnections between the radiator elements 13 and feed lines 47, 48 willbe dictated by the type of antenna operation desired. For example, inone pattern, it may be desirable to connect successive radiator elements13 located on one side of feed lines 47, 48 alternately to feed lines47, 48. Thus, every other one of the radiator elements 13 lying on oneside of the feed lines will be connected to in common to the same feedline.

Referring to FIGS. 8 and 9, it will be readily evident that the innerends of each radiator element are formed to provide a loop 49 by merelyclamping a swage fitting 51 about the bitter .ends 52, 53 of portions14, 16.

Thus, loop 49 engages a stirrup 54 which, in turn, is bolted to one endof an insulative spacer bar 56. In order to provide electricalconnection from feed lines 47, 48 to the radiator elements 13, swageconnections 57 are carried by the feed lines, such as 47, and, in turn,bolted to a connector tab por tion 58 of stirrup 54. In this manner,electrical connection is positively made between feed lines 47, 48respectively to the inner ends of each radiator element 13.

Means serving to reduce the Q of the radiators by drawing theirrespective portions 14, I6 apart whereby, for comparable performance, asmaller radiating array can be employed includes the interradiatorconnectors 62 (FIG. comprised, for example, simply of an insulator bar63 of suitably rigid insulative material such as noted above.

The opposite ends of each bar 63 are coupled to straps 64, 66 wherebyeach strap 64, 66 respectively engages a bight of a portion 16, 14 ofadjacent radiator elements 13.

Each connector assembly 62 forms an interconnecting point whereby all ofthe points lying on one side of feed lines 47, 48 define line 29 lyingin a region generally in a middle zone between the opposite ends of eachradiator element 13.

' At the leading end of array 12, the ieadingmost radiator element 13bis supported in the foregoing manner by one of the interradiatorconnectors 62 and by the means shown in FIG. 7 is carried by the leadingsupport spar 67. Thus, a rigid insulator bar 68 is supported by a U-bolt69 stone and and employs a shsckle 71 at the other end to engage theradiator portion I6 of element l3b.

At the rear end or "back" of array 12, a parasitic element 72 serves totension the rear portion of feed lines 47, 48 while the rear half of therearmost radiator element 13c may extend straight across the array inits natural position since the drawing of the forward half of suchelement provides sufficient spacing between the two conductive portions14, 16 of element [3c to permit the elimination of means for drawingaway the rear portion.

According to another embodiment, as shown in FIG. I3, a radiating array76 of similarly arranged diamond-shaped radiating elements 77 isoriented in a single upright plane as distinguished from thesubstantially horizontal plane shown in FIG. I. Thus, rather than tocarry the radiating array atop a support tower, such as tower l1, it maybe desirable under certain circumstances to provide a so-called curtain"antenna arrangement wherein the array is oriented upright.

Referring to FIG. 13, a support tower 78, suitably guyed by lines 79supports array 76 by means of a single catenary cable 81 carried betweenthe upper end of tower 78 and the upper end of a support post 82. In theregion of post 82, a balun 83 is electrically coupled to the feed lines84, 86. Support means for carrying the inner and outer ends of eachradiator element 77 are similar to those shown in the embodiment in FIG.1 and need not be repeated at this time.

A further embodiment of the invention is shown in FIGS. 10 and II and 12wherein each radiator element 87 includes a rigid spreader link 88 whichcompletes the interstices otherwise found in the line of support 29defined by the interconnecting points formed between adjacent radiatorelements. In this manner, the substantial equivalent of an interiorsupporting cable or catenary as defined by line 29 serves to provideadditional catenary cable support to the array of elements 13 to provideadvantages which are disclosed in copending US. application Ser. No.648, 475 assigned to the assignee herein.

The links 88 are preferably of a nonconductive material. If made ofconductive material, the material of the links 88 should be the same asthe radiator elements to avoid any problems of electrolysis.

Means for introducing the links 88 into line 29 appear in FIGS. 11 and12 in more particular detail. Thus, each link 88 is engaged at itsopposite ends by opposed pairs of U-shaped clamps 91 bolted thereto in amanner to retain a bight of one of the portions 87a, 87b of a radiatorelement 87 (FIG. 10). In addition, and to provide the interconnectionbetween adjacent radiators 87, rigid connecting bar 92, comparable tobar 63, (noted in parenthesis) is bolted to the opposed ends of the twopairs of clamps 91.

In the foregoing way, a major portion of the load of the array carriedby the catenary cable means may be supported by the interior supportingcable defined by the alternately occurring rigid spreader links 88 andinterradiator connecting bars 92. Thus, as shown in phantom lines inFIG. 2, a rigid spreader link 94 (comparable to bars 92) may serve tocomplete the foregoing style of interior catenary cable" as defined bythe links and interconnecting bars.

The foregoing arrangement serves to provide an overall array occupyingless land space while providing comparable performance.

From the foregoing, it will be readily apparent that a radiatingconstruction has been provided wherein the radiating elements arecomprised as a four-sided flexible configuration including opposed pairsof corners. All the radiators are oriented to lie in a single common"plane" (to the extent that the sagging nature of the arrayelements maybe considered to form a plane), and the predetermined spacing betweenthe corners of one pair is sufficient to substantially reduce the Q ofthe radiator element associated therewith so as to permit a reduction inthe array size while obtaining comparable performance.

Iclaim:

I. In an antenna structure, a radiating array of elongated radiatingelements having first and second ends thereof, feed line means operablycoupled to a first end of each of said radiating elements, and meanscommon to and supporting a plurality of said radiating elements atsecond ends thereof,

each of said radiating elements including a pair of elongated laterallyspaced radiating portions, and means interconnecting adjacent portionsof adjacent radiating elements at a position intermediate said first andsecond ends thereof to maintain a predetermined spacing between theportions of each of a plurality of said radiators, the last named meanscausing said spacing to be at its greatest in an intermediate zonebetween the first and second ends of the radiators to reduce the Q ofthe radiators.

2. In an antenna having a support tower and a radiating array carried bythe tower, said array including a plurality of spaced elongated flexibleradiator elements, each element including a pair of elongated flexibleportions, laterally spaced, flexible catenary cable means supportingouter ends of said radiator elements, feed line means coupled to theinner ends of said elements, and means for interconnecting adjacentradiator elements along a line intermediate the outer and inner ends ofsaid elements to provide a predetermined spacing between the saidportions of radiators, said spacing being at its greatest intermediatethe outer and inner ends of said radiators.

3. In an antenna according to claim 2 wherein points of interconnectionare defined between the last named means and the radiator elements atlocations between the inner and outer ends thereof, said points ofinterconnection serving to draw on of said portions of each pair ofradiator elements relatively away from the other in supporting saidelements whereby said line of interconnections acting through said oneof each pair of portions serves to efiectively broaden the radiatorsintermediate the inner and outer ends of said radiator elements toprovide said predetermined spacing.

4. In an antenna construction according to Claim 3 wherein said cablemeans includes a pair of laterally spaced cables serving to support theouter ends of radiator elements, said radiator element portions servingto define polygonal areas constituting a radiator element, saidpolygonal areas being disposed substantially in a common plane, cornersof said polygonal areas forming single points of support for connectionwith respect to said catenary cable means and said feed line means atthe inner and outer ends of the radiator elements.

5. in an antenna according to claim 3 further including a spacerdisposed between the pair of portions of each radiator element at saidpoints of interconnection to provide a line of support for said arrayintermediate the ends of each radiator element.

6. In an antenna structure, a radiating construction comprising aplurality of radiators, each of said radiators including means forming afour-sided configuration lying substantially in a single plane withfirst and second pairs of opposed comers, feed means operatively coupledat one comer of said first pair of comers, means supporting a number ofsaid radiators to form a log periodic array in which all of theradiators lie sub stantially in a single plane common to each, saidsupport means including means for maintaining a predetermined spacingbetween said second pair of corners, the spacing between said secondpair of corners being sufficient to substantially reduce the Q of theradiator.

